The present invention relates to a scroll-type compressor having a fixed scroll and a movable scroll.
A scroll-type compressor includes a fixed scroll and a movable scroll. The fixed scroll includes a fixed volute wall on its base plate. The movable scroll includes a movable volute wall on its base plate. Sealed spaces are formed between the fixed scroll and the movable scroll. The volumes of the sealed spaces vary in accordance with an orbital motion of the movable scroll.
The sealed spaces converge toward the inner ends of the volute walls of the fixed and movable scrolls. The compressed gas in the sealed spaces applies a force (thrust load) that separates the movable scroll from the fixed scroll. If the thrust load is too strong, the movable scroll is strongly pressed against a thrust bearing. This increases the force required to move the movable scroll, which applies excessive load to the mechanism that causes the movable scroll to orbit and lowers reliability of the mechanism.
In a scroll-type compressor described in Unexamined Japanese Patent Publication No. 6-74164, counter pressure is applied to the back of the movable scroll to oppose the thrust load, which prevents the movable scroll from being strongly pressed against the thrust bearing.
However, it is difficult to determine the level of the counter pressure. If the counter pressure is too strong, the distal end of the movable volute wall is strongly pressed against the base plate of the fixed scroll. This increases the force required to orbit the movable scroll and applies an excessive load to the orbiting mechanism.